In the southern sky, situated about 4,300 light years from Earth, lies RCW 120, an enormous glowing cloud of gas and dust. This cloud, known as an emission nebula, is formed of ionized gases and emits light at various wavelengths. An international team led by West Virginia University researchers studied RCW 120 to analyze the effects of stellar feedback, the process by which stars inject energy back into their environment. Their observations showed that stellar winds cause the region to expand rapidly, which enabled them to constrain the age of the region. These findings indicate that RCW 120 must be less than 150,000 years old, which is very young for such a nebula.
SOFIA is an airborne observatory consisting of an 8.8-foot (2.7-meter) telescope carried by a modified Boeing 747SP aircraft. SOFIA observes in the infrared regime of the electromagnetic spectrum, which is just beyond what humans can see. For observers on the ground, water vapor in the atmosphere blocks much of the light from space that infrared astronomers are interested in measuring. However, its cruising altitude of seven miles (13 km), puts SOFIA above most of the water vapor, allowing researchers to study star-forming regions in a way that would not be possible from the ground. Overnight, the in-flight observatory observes celestial magnetic fields, star-forming regions (like RCW 120), comets and nebulae. Thanks to the new upGREAT receiver that was installed in 2015, the airborne telescope can make more precise maps of large areas of the sky than ever before. The observations of RCW 120 are part of the SOFIA FEEDBACK survey, an international effort led by researchers Nicola Schneider at the University of Cologne and Alexander Tielens at the University of Maryland, which makes use of upGREAT to observe a multitude of star-forming regions.
We can use the expansion velocity to constrain the age of the region, and find that RCW120 must be very young, less than 150,000 years. This suggests that positive feedback processes operate on very short time periods, and could potentially be responsible for the high star formation rates the universe had in its early stages.matteo luisi
Using their [CII] observations from SOFIA, the
research team found that RCW 120 is expanding at 33,000 mph (15 km/s), which is
incredibly fast for a nebula. From this expansion speed, the team was able to
put an age limit on the cloud and found that RCW 120 is much younger than
previously believed. With the age estimate, they were able to infer the time it
took for the star formation at the boundary of the nebula to kick in after the
central star had been formed. These findings suggest that positive feedback
processes occur on very short timescales and point to the idea that these
mechanisms could be responsible for the high star formation rates that occurred
during the early stages of the universe.
Looking forward, the team hopes to expand this type of analysis to the study of more star forming regions. Matteo says, “The other regions we are looking at with the FEEDBACK survey are in different stages of evolution, have different morphologies, and some have many high-mass stars in them, as opposed to only one in RCW 120. We can then use this information to determine what processes primarily drive triggered star formation and how feedback processes differ between various types of star-forming regions.”
Matteo is a postdoctoral researcher in
the West Virginia University Department
of Physics and Astronomy and in the Center for Gravitational Waves and Cosmology.
He studies how the most massive stars in our Galaxy interact with their
environments. His collaborators on this project include researchers from West
Virginia University, the Green Bank Observatory, the University of Cologne, the
Max-Planck Institute for Radio Astronomy, Aix-Marseille University,
Pennsylvania State University, the University of Maryland and Leiden
Media Contact: Holly Legleiter
Public Relations Coordinator,
Center for Gravitational Waves and Cosmologyhlegleiter@mail.wvu.edu